I think a cap is still useful.  [...] I am much more in favor of raising the cap possibly to 10 MB (or even 5MB) to buy us the community the time to fully analyze all the possible implications of future block sizes (no cap, floating cap, high fixed cap, etc). 

If unlimited size is too worrying then the simplest safety net would be max block size = 10x median block size during previous 2016 blocks or previous difficulty period.